"Kirk Stant" wrote in message
om...
"Bill Daniels" wrote in message

The thermal entry stall/spin only requires that the pilot hold
into-the-turn
rudder a second or two longer than needed while trying to reduce
airspeed
still further. In most cases, this is a full cross-controlled
accelerated
stall from a 45 degree bank - wheee! (I've caught some high time pilots
with this one.)

Bill Daniels

Interesting exercise. Also sounds like a good way to teach
low-G/low-AOA affects on stall speeds. I can see how it would work
well in something like a Blanik, with a huge elevator. How do
competition ships with small elevators react? I'll have to try with
my LS6, but I have the feeling that the elevator is not powerful
enough to keep the nose from falling through and causing a stall/spin.

On the other hand, in the same nose high/close to stall speed
situation, the LS6 (and any other glider, I'm sure) reacts perfectly
well to an unloaded (low-G) roll in the direction of the intended
turn, followed by an easy nose down acceleration to a safe speed
before pulling on the G necessary for the turn. Not a recommended
normal thermal entry by any means, but a way to recover from a
botched, overenthusiastic zoom-in.

The obvious key is the G (or AOA) versus airspeed relationship.
Trying to turn when the airspeed is down in the teens would show that
the pilot has a certain lack of situational awareness!

Kirk
66

A stall occurs only when the AOA exceeds about 16 degrees for most airfoils.
Low G, by itself, isn't dangerous and, in fact, reduces the stall speed
since the wing isn't loaded. The stalling AOA comes in at the transition
from low G to one G.

Most competition ships fly with the CG well aft so, even with small
elevators, they have plenty of elevator authority for some interesting
stalls. I do worry that many competition pilots get very close to a
stall/spin departure without realizing it during an aggressive thermal
entry. This is particularly dangerous when down low (I've GOT to center
this thermal or land out.) Desperately and aggressively trying to center a
small core when under the stress of a pending outlanding is a bad
combination - there have been a more than a few bad outcomes to this
situation.

Bill Daniels